1. Field of the Invention
This invention relates to a liquid crystal display device. More particularly, the invention relates to a liquid crystal display device, a fabricating method, and a driving method thereof that improve visibility and reduce power consumption as well as reduce fabricating costs.
2. Description of the Related Art
Generally, a liquid crystal display device LCD controls light transmittance of liquid crystal cells in accordance with video signals to display a picture. Such an LCD implementation typically includes an active matrix type LCD having a switching device for each cell. Such LCD display devices are used as computer monitors, office equipment, cellular phones and the like. The switching device for the active matrix LCD mainly employs an array of thin film transistors (hereinafter, referred to as “TFTs”).
FIG. 1 illustrates a related art LCD driving apparatus.
Referring to FIG. 1, the related art LCD driving apparatus includes a liquid crystal display panel 52 having m×n liquid crystal cells Clc arranged in a matrix type, m data lines D1 to Dm and n gate lines G1 to Gn crossing each other and thin film transistors TFT provided at the crossings, a data driver 64 for applying data signals to the data lines D1 to Dm of the liquid crystal display panel 52, a gate driver 66 for applying scanning signals to the gate lines G1 and Gn, a gamma voltage supplier 68 for supplying the data driver 64 with gamma voltages, a timing controller 60 for controlling the data driver 64 and the gate driver 66 using synchronizing signals from a system 70, a direct current to direct current converter 74 (hereinafter a “DC/DC converter”) for generating voltages supplied to the liquid crystal display panel 52 using a voltage from a power supply 62, and an inverter 76 for driving a back light 78.
The system 70 applies vertical/horizontal synchronizing signals Vsync and Hsync, clock signals DCLK, a data enable signal DE, and R, G and B data signals to the timing controller 60.
The liquid crystal display panel 52 includes a plurality of liquid crystal cells Clc arranged in a matrix at the crossings of the data lines D1 to Dm and the gate lines G1 to Gn. The thin film transistor TFT provided at each liquid crystal cell Clc applies a data signal from a corresponding data line D1 to Dm to the liquid crystal cell Clc in response to a scanning signal from the gate line G. Further, each liquid crystal cell Clc is provided with a storage capacitor Cst. The storage capacitor Cst is provided between a pixel electrode of the liquid crystal cell Clc and a pre-stage gate line, or between the pixel electrode of the liquid crystal cell Clc and a common electrode line, to thereby maintain a constant voltage on the liquid crystal cell Clc.
The gamma voltage supplier 68 applies a plurality of gamma voltages to the data driver 64.
The data driver 64 converts R, G, and B digital video data into analog gamma voltages (i.e., data signals) corresponding to gray level values in response to a control signal CS from the timing controller 60, and applies the analog gamma voltages to the data lines D1 to Dm.
The gate driver 66 sequentially applies a scanning pulse to the gate lines G1 to Gn in response to a control signal CS from the timing controller 60 to thereby select horizontal lines of the liquid crystal display panel 52 supplied with the data signals from data driver 64.
The timing controller 60 generates the control signals CS for controlling the gate driver 66 and the data driver 64 using the vertical/horizontal synchronizing signals Vsync and Hsync and the clock signal DCLK input from the system 70. Herein, the control signal CS for controlling the gate driver 66 includes a gate start pulse GSP, a gate shift clock GSC and a gate output enable signal GOE, etc. Further, the control signal CS for controlling the data driver 64 includes a source start pulse SSP, a source shift clock SSC, a source output enable signal SOE, and a polarity signal POL, etc. The timing controller 60 re-aligns the R, D and B data from the system 70 to apply them to the data driver 64.
The DC/DC converter 74 boosts or drops a 3.3V input voltage from the power supply 62 to generate a voltage supplied to the liquid crystal display panel 52. Such a Dc/DC converter 72 generates a gamma reference voltage, a gate high voltage VGH, a gate low voltage VGL and a common voltage Vcom, etc.
The inverter 76 drives the backlight 78 with the aid of a driving voltage Vin supplied from any one of the power supply 62 and the system 70. The backlight 78 is controlled by the inverter 76 to thereby generate a light and illuminate the liquid crystal display panel 52.
A problem associated with the related art is that light output from the backlight 78 is constant. As such, if ambient light is greater than the panel brightness, panel visibility is reduced. Conversely, if the ambient light is low, then the panel may be overly bright in comparison. This excessive panel brightness in low ambient light conditions leads to unnecessary and excessive power consumption To solve this problem, a technique that senses an external light using a photosensor such as a photodiode, etc., and controls brightness of the backlight 78 by a user's operation in accordance with the photosensor output has been suggested. However, the addition of a separate photosensor increases assembly costs of the LCD panel.
Referring to FIG. 2, a technique that senses the external light 53 using a photosensor and controls brightness of the backlight in accordance with the result adjusts brightness of the backlight supplied to the entire liquid crystal display panel 52. Such related art solutions cannot selectively increase brightness of the backlight at a specific area of the liquid crystal display panel 52. Further, the external light 53 that illuminates a portion of the liquid crystal display panel 52 creates a problem in that the contrast ratio of the illuminated area (hereinafter, referred to as “illumination area”) P1, which is illuminated by the external light 53, is reduced relative to the area (hereinafter, referred to as “non-illumination area”) P2, which is not illuminated the external light 53.